Common themes in the proceedings of the first Consultation on Interactions of Pacific Tuna Fisheries

Richard S. Shomura
Hawaii Institute of Marine Biology, University of Hawaii
P.O. Box 1346
Kaneohe, Hawaii 96744 USA

ABSTRACT

Studies of tuna interaction include examination of fishery statistics, tag-and-recovery data, and the use of models. A review of the proceedings of the First FAO Expert Consultation on Interaction of Pacific Tuna Fisheries noted the difficulty in demonstrating the existence of interaction between and among tuna fisheries. Key factors appear to be the lack of appropriate fishery data, insufficient information on the biology and population dynamics of the species, and a lack of understanding about the influence of the environment on tuna resources.

1. INTRODUCTION

The marked increase in tuna landings in the Pacific during the past decade has raised the issue of interactions between and among fisheries. Pacific island nations have been especially concerned with impacts associated with their domestic fisheries in a context of providing distant water fishing nations access to their Exclusive Economic Zones (EEZ). An international meeting to review tuna interactions in the Pacific was held in Noumea, New Caledonia, from 3-11 December 1991. The meeting reviewed the status of the tuna resources in the Pacific and discussed in detail studies on tuna interaction; the proceedings of this meeting were published in two volumes (Shomura et al., 1994).

The present paper reviews the interaction studies included in the Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries (Shomura et al. 1994) in order to elicit common themes in methodology applied to interaction studies and to gain some insight on the types of problems involved in tuna interaction.

2. RESULTS

Excluding the species synopses and descriptions of fisheries, there were 20 papers on tuna interaction included in the proceedings. The general breakdown of the 20 papers was one classification of types of interaction, 15 full papers and 4 abstracts¹ on tuna interaction.

¹ Full papers have been published elsewhere.

Type A - Competition for fish at the same stage in their life cycle in the same general area by two or more fisheries,

Type B - The effect of fishing a stock at an early stage in its life cycle upon a fishery that exploits the stock at a later stage, typically with a different gear, and

Type C - The effect of fishing a stock in one area upon a fishery that exploits the stock elsewhere.

The most common thread noted throughout the proceedings was the difficulty that researchers encountered in providing proof of interaction. This difficulty was due to inadequate data, insufficient knowledge of the biology and population dynamics of the resource, and the lack of understanding the influence of the environment on tuna resources. Researchers in several studies were able only to allude to the possibility of interaction. Muhlia-Melo (1994) suggested a possible predator-prey interaction between small tunas (Auxis spp.) and yellowfin tuna in the eastern Pacific, while Naamin and Bahar (1994) examined catch trends of longline-caught yellowfin in the eastern Indian Ocean and western Pacific, and suggested a possible linkage and interaction of yellowfin between the two areas. No statistical evidence was provided due to the lack of adequate data. In many of the interaction papers, authors pointed to shortcomings in data including the lack of standardized data (Suzuki, 1994), access to data (Hampton, 1994), collection of basic data, e.g., effort statistics (Boggs, 1994), and problems with species identification (Suzuki, 1994; Bayliff, 1994).

The only direct evidence of interaction described in the proceedings resulted from tagging studies. Several authors used results of directed tagging studies to demonstrate interaction. These included skipjack in the Atlantic (Kleiber and Fonteneau, 1994), South Pacific albacore (Murray, 1994), and southern bluefin tuna (Polacheck, 1994). The occurrence of gillnet markings on troll-caught albacore gave direct evidence of interaction between the troll fishery and the high seas gillnet fishery in the North Pacific (Bartoo et al., 1994) and South Pacific (Murray, 1994).

Table 1. Summary of tuna interaction by methodology and species.

Fisheries Data and Statistics	Tagging	Modelling
Skipjack	Skipjack · Kleiber and Fonteneau (Atl.) · Hampton (ref. Kleiber et al., 1984; W. & C. Pac.) · Hampton [ref. projected study in Solomon Islands]	Skipjack · Kleiber and Fonteneau (Atl.) · Hampton (ref. Kleiber et al., 1984; W. & C. Pac.) · Hampton (ref. projected study in Solomon Islands)
Yellowfin · Boggs (Hawaii) · Suzuki (W. & C. Pac.) · Medley (W. & C. Pac.)	Yellowfin · Naamin and Bahar (Indonesia)	Yellowfin · Deriso et al. (E. Pac.)
Bigeye · Miyabe (ocean-wide)	Bigeye	Bigeye
Albacore · Murray (S. Pac.)	Albacore · Bartoo et al. (N. Pac.)	Albacore · Kleiber and Baker (N. Pac.)
Northern Bluefin · Bayliff (N. Pac.)	Northern Bluefin · Bayliff (N. Pac.)	Northern Bluefin
Southern Bluefin · Polacheck (all oceans)	Southern Bluefin · Majkowski et al. · Polacheck (all oceans)	Southern Bluefin
Small Tunas · Yesaki (Gulf of Thailand) · Muhlia-Melo (Mexico)	Small Tunas	Small Tunas
Non-species-specific · Kleiber (classification) · Hearn and Mazanov (modelling) · Sibert and Fournier (modelling) · Salvadó (modelling)

While tagging provided some direct evidence of interaction, several authors noted problems associated with the use of tagging data. These problems included (a) tagging mortality, (b) tag loss, (c) non-reporting of tag recoveries, (d) uneven distribution of tag releases, (e) lack of fishing effort in some areas of species distribution, (f) high cost of tagging experiments, and (g) the generally extended time taken to implement tagging experiments. While some of these factors were accounted for in the studies, the uncertainties of tag-and-recovery data added another dimension to the extensive “background noise” associated with interaction studies. Possibly the most crucial evidence that tagging data should be used with caution was provided by Bayliff (1994). In his review of interaction with the northern bluefin tuna, Bayliff (1994) noted that northern bluefin tagged over several successive years showed different movement patterns. This variability makes it difficult to draw definitive conclusions or to develop realistic models.

While there is substantial information of the biology of the principal commercial tuna species, several authors noted specific data needs in interaction studies. These included a better understanding of surface and subsurface-caught yellowfin tuna, age and size data for several tuna species, stock structures, and general and specific movement characteristics.

In attempting to interpret fishery data and tag-and-recovery information, researchers noted the lack of understanding of the environment influences tuna resources. Suzuki (1994) suggested that a better understanding of the environment, e.g., the influence of El Niño-Southern Oscillation events, may help to explain changes noted in catch rates. The El Niño is especially important to the tropical tuna species since its influence extends across the ocean basin, changing the thermal structure and circulation pattern. These changes influences the movement of water (Niiler, 1993) and the availability and catchability of tunas. Recently, researchers have directed effort to long-term environmental changes and their influence on fishery resources (Polovina et al., 1994).

Kleiber (1994) noted the problems associated with fishery data and tag-and-recovery information in characterizing interactions of tuna fisheries. Considering the many human and environmental factors involved in tuna fisheries, Kleiber suggests the use of dynamic models to better understand fishery response to changing conditions. He notes that an important feature of modelling is the ability to consider “confounding factors that cannot be controlled in the real world”. The use of models to understand interaction is an important iterative process. The model builder initially utilizes available estimates of resource and environmental parameters; subsequently a range of values is used to determine sensitivity of the parameters. These results, thus, provide some guidance to researchers of future information needs. As new data are collected the model is revised and the process repeated.

3. SUMMARY

The proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries highlighted the difficulties in quantifying interactions. While improvements in the collection of fisheries statistics will lead to better assessments of interaction, it appears that development of suitable dynamic models will provide the mechanism to best understand the full process. The models identify critical parameters that need to be further investigated.

4. REFERENCES CITED

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Bartoo, N., D. Holts, and C. Brown. 1994. Evidence of interactions between high seas drift gillnet fisheries and the North American troll fishery for albacore. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 214-227.

Bayliff, W.H. 1994. Interactions among fisheries for northern bluefin tuna, Thunnus thynnus, in the Pacific Ocean. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 249-263.

Boggs, C.H. 1994. Methods for analysing interactions of limited-range fisheries: Hawaii's pelagic fisheries. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 74-91.

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Kleiber, P., and A. Fonteneau. 1994. Assessment of skipjack fishery interaction in the eastern tropical Atlantic using tagging data. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 94-107.

Kleiber, P., A.W. Argue, J.R. Sibert, and L.S. Hammond. 1984. A parameter for estimating potential interaction between fisheries for skipjack tuna (Katsuwonus pelamis) in the western Pacific. Tech. Rep. Tuna Billfish Assess. Programme, S. Pac. Comm. (12): 11 p.

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Naamin, N., and S. Bahar. 1994. Interaction in the yellowfin tuna fisheries of the eastern part of Indonesian waters. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 199-212.

Niiler, P. 1993. The global surface velocity programme. Scripps Institution of Oceanography, La Jolla, California. 21 p.

Polacheck, T. 1994. An overview of interaction issues among the fisheries for southern bluefin tuna. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 264-298.

Polovina, J.J., G.T. Mitchum, N.E. Graham, M.P. Craig, E.E. DeMartini, and E.N. Flint. 1994. Physical and biological consequences of a climate event in the central North Pacific. Fish. Oceanogr. 3(1): 15-21.

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Suzuki, Z. 1994. A review of interaction between purse seine and longline on yellowfin (Thunnus albacares) in the western and central Pacific Ocean. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 158-181.